In August this year I nominated to join the board of BHP Billiton, the world’s largest diversified resource company, on the basis that the company needs to take far more extensive and urgent action to address climate change and its potentially destructive impact on BHP’s shareholder value. BHP maintains it is well aware of climate change risk and is taking appropriate action; accordingly, the board has recommended that shareholders vote against my appointment. So why pursue this course?

Over the past 20 years it has become evident that conventional politics in Western democracies will never provide the leadership necessary to address climate change. The recent Australian election, the denialist stance of the Abbott government and the ineffectiveness of its ALP predecessors just rams the point home. It is impossible for politicians driven by short-term electoral considerations and ideological paranoia to take a balanced view on an all-pervasive, existential issue like climate change.

However, as Voltaire put it: “Men argue, Nature acts.” The latest science confirms that fossil-fuel emissions from human activity are warming the planet at an accelerating rate, and that both the extent and speed of that warming have been badly underestimated.

Current climate policies are leading to a world with an average temperature increase in excess of 4 degrees above pre-industrial levels — a world where population would fall from the current 7 billion to below 1 billion, caused by a combination of heat stress, escalating extreme weather disasters, sea level rise, disease, food and water scarcity, and consequent social disorder and conflict. Early signs of this are already evident in the conflicts in Egypt and Syria, where climate change has been a significant contributing factor.

These impacts are being locked in by our investment decisions and inaction today, but the full, catastrophic effect will only evolve over time. Typhoon Haiyan sadly is providing a foretaste.

Dangerous climate change is already happening at the 0.8-degree temperature increase we are experiencing now. The “official” limit of 2 degrees now represents the boundary between dangerous and extremely dangerous climate change. To have a reasonable chance of staying below even the 2-degree limit, we have virtually no carbon budget left to burn, not even the 20% of global proven fossil-fuel reserves frequently quoted. To avoid catastrophic outcomes we must take emergency action now to halt new fossil-fuel investment, and rapidly wean ourselves off established fossil-fuel use.

In the absence of political leadership, business in its own self-interest must act — business as we know it in a world that is 4 degrees hotter is not possible.